Ethiopia Chocolate and Crystal Shewa Province Nodule Opal
In 1939 the famous anthropologist Dr. L. Leakey reported that early man used opal to fashion tools based on a discovery of artifacts in a cave in Kenya that were dated from around 4,000 years B.C. and so believed that opal mines must exist in Africa. In was not until much later in 1994 that actual proof of these opals came to light with a Dr. N. Barot who reported in an article in the ICA Gazette that opals from Ethiopia had been seen at a Nairobi gem market in 1993. In the same year a minerals engineer by the name of Telahun Yohannes learned about these opals while on holiday and started investigating its location along with a lease to explore and mine the area. And that begins the start of a new and stunningly beautiful opal onto the market.
The Chocolate Nodule opals are found at Yita Ridge, in the Menz Gishe District of Shewa Province, around 150 miles northeast of Addis Ababa, the capital of Ethiopia. The opal field lies around 12 miles north of Mezezo and extends for several square kilometers along the northern side of the Yita Ridge.
The opals are found in a nodular form within a continuous layer of welded volcanic ash (tuff, similar to obsidian in character), about 3 metres thick, that lies between weathered rhyolite layers. The nodules are very numerous though in my opinion the percentage of gem precious opal is quite small. In 1997 out of 10 kilos of un-opened nodules I acquired I found only one with good precious opal, around 20 with some colour play and the rest were either empty, filled with common opal or quartz. Figures in 1995 estimated that around 15% of the opal recovered was gem quality, and around 1% shows distinct play of colour.
Good Ethiopian opals are quite diverse including red, orange, clear, white, grey, black, yellow, blue, brown and green. The play of color shows in the usual way or as a contra-luz, when held against a light. The best pieces show vivid play of color usually with the full color spectrum as well as turquoises and indigos.
You can see from our stock that this material can be polished. However it should be noted that a lot of the opals do in fact show internal fractures and crazing that in my opinion do not detract from their beauty some opals that have been cut and show no fractures at all.
It is still relatively early days in the exploration of these opals and cutters are finding new techniques and ways to bring these beautiful opals to the market. The photographs will never do these opals justice, so if you are interested you need to find the real things to discover just how amazing they are.
Gems & Gemmology magazine Summer 1996
Crystal vine UK
Lapidary Journal, July 1996